The present invention relates to a method of weatherproofing surfaces, particularly roofs, and to surfaces weatherproofed in accordance with the method. The invention is particularly useful in cold-process roofing, and is therefore described below with respect to this application.
Cold-process roofing, which has been used for many years particularly in the United States of America, is a process for applying a built-up asphalt (bitumen) roof without the necessity of heating the asphalt on the job. In this process, a cold-process cement is used for bonding one or more plies of an asphalt-saturated-felt to the roof. The asphalt-saturated-felt used in this process must meet a number of requirements: Thus, it must provide an outer surface which is hard or to which a top surface material, if used, will firmly adhere; it must provide a surface to which the cold-process cement will also firmly adhere; and it must allow the solvent of the cold-process cement to evaporate through it so that the cement sets up properly to form a tight water-proof bond. The cold-process cement must also meet certain requirements: Thus, it must be of a material which can be easily applied to form a continuous film; it must firmly bond a ply of a cold-processed felt to the roof deck, and additional plies together if a plurality of plies are used; and it must set-up rapidly, that is within 24 hours under normal spring or fall weather conditions, to firmly bond the felt against slippage.
To meet these requirements, the cold-process felt, which may be of mineral fibers (e.g., asbestos, glass) or of organic fibers (e.g., paper, rags, wood), and which is sometimes called a mat particularly when of fiber-glass, is usually saturated with asphalt such as to have an outer surface of a hard asphalt, e.g., one having a softening point (sometimes referred to as Ball and Ring Number) of at least 180.degree. F. This may be done by saturating the felt with the hard asphalt material, or saturating it with a soft asphalt material and providing outer face coatings of the hard asphalt material. The cold process cement used is usually a hard asphalt (typically an air-blown asphalt of 195.degree. F. softening point) present to about 50% by weight of the total composition, mineral fibers present to about 10% by weight, and a solvent (usually 300.degree.-400.degree. F. boiling range naphtha) present to about 40% by weight. Providing a hard, high softening point asphalt in such cold-process cements is usually considered necessary to prevent the roofing from slipping or sliding, and even then the maximum acceptable slope for such roofings is considered to be two inches per foot, unless mechanical fastening devices are used to supplement the holding of the cement itself.
In addition to the maximum slope permissible in the use of such cold-process cements, these cements also form a tight membrane film which is very low in moisture vapor transmission. The roofing is therefore subject to blistering by moisture trapped below the roofing. This problem is particularly serious when the roofing is applied to concrete surfaces where vapor is released from the concrete for a long drying-out period.
A number of techniques have been developed in an attempt to counteract the above-mentioned blistering problem, but these techniques have not proved entirely satisfactory. Thus, water emulsions of the asphalt have been developed, but these have been found feasible for top surfacing only; moreover since they are water-based materials, they are subject to freezing at low temperatures, and to washing-off by rain before they are thoroughly set. Roofings have also been devised including regularly-spaced adhesion points, rather than continuously bonded films, to permit the escape of vapor and thereby to prevent blistering; but such techniques are usually expensive to apply, and moreover, they have not successfully overcome the maximum-slope limitation mentioned above.